A freshman GOP congressman on the House Homeland Security Committee is telling President Obama he’s “game” for building an alligator-filled moat along the U.S.-Mexico border to counter illegal immigration.

“I actually think a moat might be a very good idea and I’m wondering how many alligators it would take to secure the entire border,” Rep. Joe Walsh says in a May 11 letter to Obama.

The president initially voiced the idea to mock Republicans who he said are never satisfied with how secure the border is, despite steps he’s taken to add security such as increasing the number of border patrol agents.

“Maybe they’ll need a moat,” he said, “Maybe they want alligators in the moat.”

Walsh says he’s “game.”

The letter carries a satirical edge — spokesman Justin Roth described it as a “tongue-in-cheek kind of thing.” Still, Roth insisted, Walsh is deadly serious about enforcing border security and was “infuriated” by Obama’s mockery.

“When you consult with Latino Hollywood celebrities such as Eva Longoria and Rosario Dawson wanting their take on immigration reform, you aren’t serious. When you sit down with the SEIU and other union leaders to get their take on immigration reform, you aren’t serious. When you threaten to sue border states that are only doing what the federal government won’t do, you aren’t being serious. And, finally, when you bring up ‘immigration reform’ for political reasons – to fire up the folks on the left as the election season nears – you aren’t serious,” Walsh tells Obama.

“When it comes to securing our borders, enforcing our immigration laws and holding businesses accountable to hiring illegal immigrants, Mr. President, I, like many of my Republican colleagues, am serious. And if it would take introducing legislation to build a moat with alligators in order to secure our borders to get you to be serious on the topic – I’m game,” Walsh says.